E-commerce accounting integration and inventory sync move orders, invoices, and stock levels between systems automatically. You can use a ready-made plugin, an integration platform (Make, Zapier, n8n), or a custom API integration. The right choice depends on your order volume, your tools, and who monitors the connection.

Manual entry wastes time and introduces errors. Below, you will find API integration explained alongside webhooks and feeds, how to map your data flows, and what to watch out for: who owns each piece of data, what happens during an outage, and what ongoing operations cost.

What manual data entry costs you

Typing data by hand costs time, breeds mistakes, and causes delays. A few orders a day are manageable, but hundreds a month take a part-time role.

Mistakes cost even more. A typo in an order number, a missed discount, or a miscounted item leads to wrong invoices, oversold stock, and hours reconciling numbers. Credit notes and apologies take longer than the order itself.

Delays hurt too. If you update stock once a night, your store shows morning numbers all day and easily sells the last items twice.

Run the math with your own numbers:

1. Your store receives 600 orders a month.
2. Entering one into accounting and deducting stock takes 3 minutes.
3. That is 1,800 minutes, or 30 hours a month.
4. Fixing mistakes takes 5 hours a month.
5. In total, you lose 35 hours a month (over 4 workdays), or 420 hours a year.

Multiply those hours by your hourly rate to see what an integration is worth. Factor in ongoing operating costs too.

API, webhook, feed, and export without jargon

APIs, webhooks, feeds, and exports are four ways systems pass data. They differ in who asks, when, and how often. Once you know them, you can check what your store or accounting software supports.

API (Application Programming Interface) works like a waiter. You place a request and get a response from the kitchen. Your store asks accounting for an invoice or checks inventory for stock. A good API specifies what you can ask for, in what format, and how often.

Webhook is a doorbell. Accounting does not have to ask for new orders every five minutes — the store rings as soon as an order arrives. Data moves right away without wasted requests.

Feed is a posted menu updated on a schedule. Typically an XML file of products, prices, and stock, it is pulled by price comparison sites or partners. It is one-way: readers cannot edit it.

Export and import are boxes of papers carried between systems now and then. An accountant might upload store invoices once a week. It is the simplest option, but it lags and relies on someone remembering.

Mapping data flows in your business

Before picking tools, sketch where data moves on paper. Each system (store, accounting, inventory, carrier, bank, Excel, email) is a box; arrows show the data passed between them.

Follow these steps:

1. List every system, spreadsheet, and inbox an order touches.
2. Draw arrows for each record: order, invoice, payment, stock level, shipment, customer.
3. Mark manual transfers. Wherever people retype or copy-paste, integration helps.
4. Spot double entry. Data typed in two places (addresses, prices) will drift apart.
5. Plan for outages. Where do orders pile up, and who notices if a system is down for an hour?

Four flows save the most time when connected:

• orders from the store to accounting,
• stock levels back to the store,
• shipments to the carrier,
• matching bank payments to invoices.

A data flow map is a strong first step toward broader business process digitization.

Who owns the data

In any e-commerce accounting integration, each piece of data needs one master system — a single source of truth. Other systems only read from it. Without this rule, store prices soon drift from accounting, and nobody knows which is right.

A typical split for a smaller store:

• Products and descriptions: online store or product information tool.
• Prices and stock: accounting or inventory system, pushed to the store.
• Orders: created in the store, passed to accounting.
• Invoices and tax records: accounting software (manages numbering and taxes).
• Customers: sign-ups in the store, company billing details verified via ARES (Czech business registry).

Why not sync everything both ways? If a record changes in two places at once, the sync may pick the wrong version or loop endlessly. Keep two-way sync strictly where needed. Define which system has the final say for every field.

A second requirement when you connect your online store to ERP or accounting is a shared identifier:

• Product: matching SKU or EAN (if the store uses "KR-50" and the warehouse "krem50ml", they will not match).
• Company: company ID (IČO in Czechia).
• Payment: payment reference matching the order or invoice number.

Unifying codes takes effort, but you do it once and prevent countless errors.

Three ways to integrate and Czech specifics

You can connect systems in three ways: a ready-made plugin, an integration platform, or custom API work. They differ in out-of-the-box features, cost, and maintenance.

Ready-made plugin is the fastest path. Major store platforms offer plugins and exports for popular accounting tools, so you can set up the basics in an afternoon. If a plugin covers most needs and you handle the rest by hand, pick this.

Integration platform (Make, Zapier, n8n) links apps visually without code. Pricing scales with usage:

• Zapier bills per task (100 free tasks/month as of November 2026),
• Make bills per credit (1,000 free credits/month),
• n8n Cloud bills per execution, and its community edition can be self-hosted.

Platforms fit simpler flows. With hundreds of daily orders and complex logic, costs and clutter grow fast.

Custom integration pays off with custom rules (wholesale tiers, multi-warehouse, returns, bundles), multiple systems, or high volume. Expect a higher upfront budget and a maintenance agreement.

Czech market specifics

• Pohoda (Czech accounting software by Stormware) connects via XML — in file batches or live via POHODA mServer. Because mServer is a built-in HTTP server, Pohoda must stay running; Stormware recommends running it on a local network, not a public IP.
• Money and ABRA Flexi (Czech ERP systems) provide their own APIs; features depend on your edition and license, so check with the vendor.
• Banking: e.g., the Fio banka API (Czech bank) pulls transactions for automatic payment matching.
• ARES: via its public API, stores auto-fill and verify Czech company billing details by ID (IČO).
• Carriers (Zásilkovna, PPL, DPD — parcel networks) offer APIs to create labels and track parcels without retyping.
• Price comparison sites (Heureka, Zboží.cz — Czech shopping portals) read product, price, and stock feeds from the same source of truth as your store.

When things break

Every integration fails eventually — from an outage, a changed data format, or an expired key. What matters is finding out in a minute rather than a month.

A reliable integration has three safeguards:

• Retries: repeats failed transfers after brief outages.
• Alerts: notifies a named person when a transfer fails.
• Logs: records transfers so you can trace what failed and why.

Watch out for rate limits and expirations. Fio banka's API docs (version 1.9, October 16, 2025) state that a token can be queried at most once every 30 seconds before returning an error. Tokens expire after at most 180 days and renew only if auto-renewal is on and someone logs into online banking. A detail like that can silently halt payment sync six months in.

Third-party changes are another risk — carriers and banks release new API versions and retire old ones. Someone has to track updates and adjust the code.

Before launch, test everything on copied data or a staging environment. Test edge cases too: returns, credit notes, promo codes, duplicate payments, and post-dispatch cancellations.

Store API keys securely, grant least privilege, and rotate them when changing vendors. Read more in our guide to cybersecurity for businesses.

Cost of e-commerce accounting integration and how to brief it

Integration costs have two parts: one-time setup and ongoing operations and maintenance, which often exceed the initial build over a few years.

Setup depends on the number of systems and flows, API quality, and edge cases (returns, credit notes, bundles, multiple warehouses). Ongoing costs cover platform or plugin fees, hosting, monitoring, and updates. Plugins follow published pricing; custom work scales with scope. Our business systems start from CZK 180,000, and an online store with inventory sync starts from CZK 140,000.

With a few dozen monthly orders and a weekly manual export, system integration will not pay back. It pays off when retyping eats hours each week, errors repeat, or delays cost you sales. For custom builds, make sure your contract gives you the source code, keys, and documentation in case you switch vendors.

A clear brief saves money:

Start with the most painful flow, usually orders to accounting. If you want to connect your store, accounting, and inventory, try our project configurator for an initial solution outline.

Frequently asked questions